The present application relates to a seat belt locking buckle that fastens a top end of a seat belt to a vehicle body in order to restrain an occupant in the event of an emergency in which a deceleration greater than a normal deceleration is applied to a vehicle, such as the event of collision (hereinafter simply referred to “in the event of emergency”), and a seat belt apparatus including the seat belt locking buckle.
Seat belt apparatuses attached to a seat of a vehicle, such as an automobile vehicle, have been designed to restrain an occupant by a seat belt in the event of emergency. Examples of such seat belt apparatuses include a three-point seat belt apparatus, which has been widely known and used. In such widely known three-point seat belt apparatus, a top end of a seat belt withdrawn from a seat belt retractor is secured to a vehicle body.
To lock the top end of a seat belt to a vehicle body, a seat belt apparatus in which the top end of a seat belt is locked to the vehicle body by latching (engaging) the seat belt locking buckle provided at the top end of the seat belt with a seat belt locking tongue fixed to the vehicle body has been developed (refer to, for example, U.S. published patent application no. 2003/0071453, incorporated by reference herein).
In a seat belt apparatus according to a first embodiment described in US2003/0071453, the seat belt locking buckle includes a pair of buckle latch members each being formed in a plate shape and rotatably disposed about a pivot axis. The two buckle latch members operate in a scissors manner. In addition, the seat belt locking tongue includes a tongue latch member formed in a plate shape. When the tongue latch member is inserted into the buckle, the pair of buckle latch members latches the tongue latch member using a biasing force of a spring.
In addition, in a seat belt apparatus according to a second embodiment described in US2003/0071453, the seat belt locking buckle includes a substantially cylindrical latch member. The latch member is formed so as to extend in a direction perpendicular or substantially perpendicular to a flat movement plane located in a trajectory region in which the tongue latch member moves in the seat belt locking buckle. In addition, the latch member is disposed so as to be rotatable about an axis extending in that direction. The substantially cylindrical latch member is always and directly urged by a biasing force of a torsion spring disposed along the axis direction of the latch member so as to be rotated in a direction toward a latch position of the tongue latch member. In addition, the seat belt locking tongue includes a tongue latch member formed in a plate shape. Under a condition in which the buckle latch member is not latched by the tongue latch member, the buckle latch member is held at a non-latch position by a holding member. If the tongue latch member is inserted into the buckle to activate the holding member, the buckle latch member is rotated to the latch position by the biasing force of the torsion spring. Thus, the buckle latch member and the tongue latch member are latchable with each other.